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  • Very long strings as primary keys in a database for caching

    - by Bill Zimmerman
    Hi, I am working on a web app that allows users to create dynamic PDF files based on what they enter into a form (it is not very structured data). The idea is that User 1 enters several words (arbitrary # of words, practically capped of course), for example: A B C D E There is no such string in the database, so I was thinking: Store this string as a primary key in a MySQL database (it could be maybe around 50-100k of text, but usually probably less than 200 words) Generate the PDF file, and create a link to it in the database When the next user requests A B C D E, then I can just serve the file instead of recreating it each time. (simple cache) The PDF is cpu intensive to generate, so I am trying to cache as much as I can... My questions are: Does anyone have any alternative ideas to my approach What will the database performance be like? Is there a better way to design the schema than using the input string as the primary key?

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  • perl hashes - comparing keys and values

    - by Aaron Moodie
    I've been reading over the perl doc, but I can't quite get my head around hashes. I'm trying to find if a hash key exists, and if so, compare is't value. The thing that is confusing me is that my searches say that you find if a key exists by if (exists $files{$key}) , but that $files{$key} also gives the value? the code i'm working on is: foreach my $item(@new_contents) { next if !-f "$directory/$item"; my $date_modified = (stat("$directory/$item"))[9]; if (exists $files{$item}) { if ($files{$item} != $date_modified { $files{$item} = $date_modified; print "$item has been modified\n"; } } else { $files{$item} = $date_modified; print "$item has been added\n"; } }

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  • Nhibernate: one-to-many, based on multiple keys?

    - by e36M3
    Lets assume I have two tables Table tA ID ID2 SomeColumns Table tB ID ID2 SomeOtherColumns I am looking to create a Object let's call it ObjectA (based on tA), that will have a one-to-many relationship to ObjectB (based on tB). In my example however, I need to use the combination of ID and ID2 as the foreign key. If I was writing SQL it would look like this: select tB.* from tA, tB where tA.ID = tB.ID and tA.ID2 = tB.ID2; I know that for each ID/ID2 combination in tA I should have many rows in tB, therefor I know it's a one-to-many combination. Clearly the below set is not sufficient for such mapping as it only takes one key into account. <set name="A2" table="A2" generic="true" inverse="true" > <key column="ID" /> <one-to-many class="A2" /> </set> Thanks!

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  • How to assign default values and define unique keys in Entity Framework 4 Designer

    - by csharpnoob
    Hello, I've had a look at the Entity Framework 4. While generating code for the SQL Server 2008 I came to the point where I want to define some default values for some fields. how to define in the designer for a Created DateTime Field the DateTime.Now default value? - Error 54: Default value (DateTime.Now) is not valid for DateTime. The value must be in the form 'yyyy-MM-dd HH:mm:ss.fffZ' how to make for code generation a string Field unique. Like E-Mail or Username can exists only once in the table. I've search alot in the internet and also checked my books Pro Entity Framework 4.0 and Programming Entity Framework. But none of them seems to come up with the default value issue, or using sql commands as default values for database generation. Another thing is, how to prevent on database generation always from droping tables? Instead i want to append non existing fields and keep the data. Thanks for any suggestions.

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  • cakephp filter index pages according to foreign keys

    - by Marki
    Hi there, I'm pretty new to CakePHP and was missing a crucial feature not generated as scaffold: filtering. What do I have to do to provide dropdowns or multi-selects on the index pages for each field that is a (foreign) key, thereby allowing to filter the table ("OR" inside multi-select, "AND" between different multi-selects, if any)? From what my websearch has shown me there are many more people trying to accomplish the same thing, although I couldn't find anything that would work for me because either they have text fields and do wildcard filtering, or the plugins they propose only work for 1.2 whereas i now started with 1.3 etc. etc. Can someone alleviate the confusion and maybe present some working code or direct me to the definitive guide[tm] where this matter has been solved? Thx

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  • NullPointerException when generating RSA keys with BouncyCastle

    - by Tom Brito
    public static void main(String[] args) throws Exception { RSAKeyPairGenerator rsaKeyPairGen = new RSAKeyPairGenerator(); AsymmetricCipherKeyPair keyPair = rsaKeyPairGen.generateKeyPair(); } the rsaKeyPairGen is not null, but the generateKeyPair() method is throwing NullPointerException. What may be wrong? Error message: java.lang.NullPointerException at org.bouncycastle.crypto.generators.RSAKeyPairGenerator.generateKeyPair(Unknown Source) at pkg.main(Main.java:154)

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  • Remove certain keys from a dictionary in python

    - by Margaret
    I'm trying to construct a dictionary that contains a series of sets: {Field1:{Value1, Value2, Value3}, Field2{Value4}} The trouble is, I then wish to delete any fields from the dictionary that only have one value in the set. I have been writing code like this: for field in FieldSet: if len(FieldSet[field]) == 1: del(FieldSet[field]) But receive the error "RuntimeError: dictionary changed size during execution". (Not surprising, since that's what I'm doing.) It's not the be-all and end-all if I have to knock together some sort of workaround, but is it possible to do this?

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  • NHibernate, legacy database, foreign keys that aren't

    - by Joe
    The project I'm working on has a legacy database with lots of information in it that's used to alter application behavior. Basically I'm stuck with something that I have to be super careful about changing. Onto my problem. In this database is a table and in this table is a column. This column contains integers and most of the pre-existing data have a value of zero for this column. The problem is that this column is in fact a foreign key reference to another entity, it was just never defined as such in the database schema. Now in my new code I defined my Fluent-NHibernate mapping to treat this column as a Reference so that I don't have to deal with entity id's directly in my code. This works fine until I come across an entity that has a value of 0 in this column. NHibernate thinks that a value of 0 is a valid reference. When my code tries to use that referenced object I get an ObjectNotFoundException as obviously there is no object in my database with an id of 0. How can I, either through mapping or some kind of convention (I'm using Fluent-nhibernate), get NHibernate to treat id's that are 0 the same as if it was NULL?

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  • Numeric operations over SHA-1 generated keys in C#

    - by webdreamer
    I'm trying to implement a Chord distributed hash table. I want to use SHA-1 as the hash function to generate node ids and map values to the DHT. However, I'll need to use numerical operations on the SHA-1 generated key, such as a modulo, for example. I wonder in which type of variable should I put the array of bytes I get, and how can I convert from one to another.

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  • Strange results - I obtain same value for all keys

    - by Pietro Luciani
    I have a problem with mapreduce. Giving as input a list of song ("Songname"#"UserID"#"boolean") i must have as result a song list in which is specified how many time different useres listen them... so a output ("Songname","timelistening"). I used hashtable to allow only one couple . With short files it works well but when I put as input a list about 1000000 of records it returns me the same value (20) for all records. This is my mapper: public static class CanzoniMapper extends Mapper<Object, Text, Text, IntWritable>{ private IntWritable userID = new IntWritable(0); private Text song = new Text(); public void map(Object key, Text value, Context context) throws IOException, InterruptedException { /*StringTokenizer itr = new StringTokenizer(value.toString()); while (itr.hasMoreTokens()) { word.set(itr.nextToken()); context.write(word, one); }*/ String[] caratteri = value.toString().split("#"); if(caratteri[2].equals("1")){ song.set(caratteri[0]); userID.set(Integer.parseInt(caratteri[1])); context.write(song,userID); } } } This is my reducer: public static class CanzoniReducer extends Reducer<Text,IntWritable,Text,IntWritable> { private IntWritable result = new IntWritable(); public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { Hashtable<IntWritable,Text> doppioni = new Hashtable<IntWritable,Text>(); for (IntWritable val : values) { doppioni.put(val,key); } result.set(doppioni.size()); //doppioni.clear(); context.write(key,result); } } and main: Configuration conf = new Configuration(); Job job = new Job(conf, "word count"); job.setJarByClass(Canzoni.class); job.setMapperClass(CanzoniMapper.class); //job.setCombinerClass(CanzoniReducer.class); //job.setNumReduceTasks(2); job.setReducerClass(CanzoniReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); System.exit(job.waitForCompletion(true) ? 0 : 1); Any idea???

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  • ubuntu gnome short cut keys

    - by benjipete
    Hi, I have done something quite silly and not sure how to fix it. I modified some of the gnome keyboard short cuts and was trying to disable the "Run Application" command. In the process I assigned it to the delete key and every time I hit delete the "Run Application" window comes up. It would not normally be a problem but the "Keyboard Shortcuts" no long has the short cut in the window so I can't disable it. Any help advice would be appreciated. Cheers Ben

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  • NullPointerException when generating RSA keys with boucycastle

    - by Tom Brito
    public static void main(String[] args) throws Exception { RSAKeyPairGenerator rsaKeyPairGen = new RSAKeyPairGenerator(); AsymmetricCipherKeyPair keyPair = rsaKeyPairGen.generateKeyPair(); } the rsaKeyPairGen is not null, but the generateKeyPair() method is throwing NullPointerException. What may be wrong? Error message: java.lang.NullPointerException at org.bouncycastle.crypto.generators.RSAKeyPairGenerator.generateKeyPair(Unknown Source) at pkg.main(Main.java:154)

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  • Setting Mnemonics and Hot Keys for a JOptionPane Dialog

    - by Daniel Bingham
    Is it possible to assign hotkeys and mnemonics to the buttons in a JOptionPane Dialog? I'd like to be able, in a JOptionPane generated message dialog with the options Yes, No and Cancel, press Y to hit the Yes button, N to hit the No button and escape to activate the escape button. Similarly in a dialog with Okay and Cancel buttons I'd like to be able to activate them with enter and escape. I've attempted passing JButtons into the JOptionPane's button Object array with the Mnemonics set already. The mnemonics work and the buttons show up correctly in the dialogs, however, they do not act properly when they are activated. Most noticeably they do not dispose of the dialog. What is the correct way to add hotkeys and Mnemonics to a JOptionPane Dialog's buttons? As always, my apologies ahead of time if this is a duplicate - I searched both Google and Stackoverflow and found nothing.

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  • Unique keys for Sphinx along three vectors instead of two

    - by Brendon Muir
    I'm trying to implement thinking-sphinx across multiple 'sites' hosted under a single rails application. I'm working with the developer of thinking-sphinx to sort through the finer details and am making good progress, but I need help with a maths problem: Usually the formula for making a unique ID in a thinking-sphinx search index is to take the id, multiply it by the total number of models that are searchable, and add the number of the currently indexed model: id * total_models + current_model This works well, but now I also through an entity_id into the mix, so there are three vextors for making this ID unique. Could someone help me figure out the equation to gaurantee that the id's will never collide using these three variables: id, total_models, total_entities The entity ID is an integer. I thought of: id * (total_models + total_entities) + (current_model + current_entity) but that results in collisions. Any help would be greatly appreciated :)

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  • Composite keys as Foreign Key?

    - by paulio
    I have the following table... TABLE: Accounts ID (int, PK, Identity) AccountType (int, PK) Username (varchar) Password (varchar) I have created a composite key out of ID and AccountType columns so that people can have the same username/password but different AccountTypes. Does this mean that for each foreign table that I try and link to I'll have to create two columns? I’m using SQL Server 2008

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  • mozilla browser hot keys? [closed]

    - by Roger22
    Hello, Where can i find the key combinations for some actions, in Mozilla Firefox? For example, Ctrl+L moves the cursor to the address bar. I wanna move the cursor in the Google search box, from the right-top position). Which key is associated with this? And some other key combinations? Thanks!

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  • Model-binding an object from the repository by several keys

    - by Anton
    Suppose the following route: {region}/{storehouse}/{controller}/{action} These two parameters region and storehouse altogether identify a single entity - a Storehouse. Thus, a bunch of controllers are being called in the context of some storehouse. And I'd like to write actions like this: public ActionResult SomeAction(Storehouse storehouse, ...) Here I can read your thoughts: "Write custom model binder, man". I do. However, the question is How to avoid magic strings within custom model binder? Here is my current code: public class StorehouseModelBinder : IModelBinder { readonly IStorehouseRepository repository; public StorehouseModelBinder(IStorehouseRepository repository) { this.repository = repository; } public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) { var region = bindingContext.ValueProvider.GetValue("region").AttemptedValue; var storehouse = bindingContext.ValueProvider.GetValue("storehouse").AttemptedValue; return repository.GetByKey(region, storehouse); } } If there was a single key, bindingContext.ModelName could be used... Probably, there is another way to supply all the actions with a Storehouse object, i.e. declaring it as a property of the controller and populating it in the Controller.Initialize.

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  • FluentNHibernate mapping of composite foreign keys

    - by Faron
    I have an existing database schema and wish to replace the custom data access code with Fluent.NHibernate. The database schema cannot be changed since it already exists in a shipping product. And it is preferable if the domain objects did not change or only changed minimally. I am having trouble mapping one unusual schema construct illustrated with the following table structure: CREATE TABLE [Container] ( [ContainerId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Container] PRIMARY KEY ( [ContainerId] ASC ) ) CREATE TABLE [Item] ( [ItemId] [uniqueidentifier] NOT NULL, [ContainerId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Item] PRIMARY KEY ( [ContainerId] ASC, [ItemId] ASC ) ) CREATE TABLE [Property] ( [ContainerId] [uniqueidentifier] NOT NULL, [PropertyId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Property] PRIMARY KEY ( [ContainerId] ASC, [PropertyId] ASC ) ) CREATE TABLE [Item_Property] ( [ContainerId] [uniqueidentifier] NOT NULL, [ItemId] [uniqueidentifier] NOT NULL, [PropertyId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Item_Property] PRIMARY KEY ( [ContainerId] ASC, [ItemId] ASC, [PropertyId] ASC ) ) CREATE TABLE [Container_Property] ( [ContainerId] [uniqueidentifier] NOT NULL, [PropertyId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Container_Property] PRIMARY KEY ( [ContainerId] ASC, [PropertyId] ASC ) ) The existing domain model has the following class structure: The Property class contains other members representing the property's name and value. The ContainerProperty and ItemProperty classes have no additional members. They exist only to identify the owner of the Property. The Container and Item classes have methods that return collections of ContainerProperty and ItemProperty respectively. Additionally, the Container class has a method that returns a collection of all of the Property objects in the object graph. My best guess is that this was either a convenience method or a legacy method that was never removed. The business logic mainly works with Item (as the aggregate root) and only works with a Container when adding or removing Items. I have tried several techniques for mapping this but none work so I won't include them here unless someone asks for them. How would you map this?

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  • Cryptography: best practices for keys in memory?

    - by Johan
    Background: I got some data encrypted with AES (ie symmetric crypto) in a database. A server side application, running on a (assumed) secure and isolated Linux box, uses this data. It reads the encrypted data from the DB, and writes back encrypted data, only dealing with the unencrypted data in memory. So, in order to do this, the app is required to have the key stored in memory. The question is, is there any good best practices for this? Securing the key in memory. A few ideas: Keeping it in unswappable memory (for linux: setting SHM_LOCK with shmctl(2)?) Splitting the key over multiple memory locations. Encrypting the key. With what, and how to keep the...key key.. secure? Loading the key from file each time its required (slow and if the evildoer can read our memory, he can probably read our files too) Some scenarios on why the key might leak: evildoer getting hold of mem dump/core dump; bad bounds checking in code leading to information leakage; The first one seems like a good and pretty simple thing to do, but how about the rest? Other ideas? Any standard specifications/best practices? Thanks for any input!

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  • Filtering foreign keys with AJAX in Django admin

    - by cnobile
    I have most of this figured out already. I have AJAX returning the region/state/province when a country is selected. The correct foreign key is saved to the database, however, when the record is viewed afterwards the selected state is not shown in the select nor are any states for the selected country. I understand why this is happening as, the admin view is not aware of the relation between the state and the country. So here is the question. Is there a hook in the admin view that will allow me to load the correct states for the country and set the selected attribute on the option in the select tag? Or how can I override the admin view for any forms that require the country and region/state/province set? I am using jQuery and Djando-1.1. Thanks

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  • Advice Please: SQL Server Identity vs Unique Identifier keys when using Entity Framework

    - by c.batt
    I'm in the process of designing a fairly complex system. One of our primary concerns is supporting SQL Server peer-to-peer replication. The idea is to support several geographically separated nodes. A secondary concern has been using a modern ORM in the middle tier. Our first choice has always been Entity Framework, mainly because the developers like to work with it. (They love the LiNQ support.) So here's the problem: With peer-to-peer replication in mind, I settled on using uniqueidentifier with a default value of newsequentialid() for the primary key of every table. This seemed to provide a good balance between avoiding key collisions and reducing index fragmentation. However, it turns out that the current version of Entity Framework has a very strange limitation: if an entity's key column is a uniqueidentifier (GUID) then it cannot be configured to use the default value (newsequentialid()) provided by the database. The application layer must generate the GUID and populate the key value. So here's the debate: abandon Entity Framework and use another ORM: use NHibernate and give up LiNQ support use linq2sql and give up future support (not to mention get bound to SQL Server on DB) abandon GUIDs and go with another PK strategy devise a method to generate sequential GUIDs (COMBs?) at the application layer I'm leaning towards option 1 with linq2sql (my developers really like linq2[stuff]) and 3. That's mainly because I'm somewhat ignorant of alternate key strategies that support the replication scheme we're aiming for while also keeping things sane from a developer's perspective. Any insight or opinion would be greatly appreciated.

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